From b9d61d202c7acebac58ce55c1da89f8e67dd29a7 Mon Sep 17 00:00:00 2001
From: Eliot Horowitz <eliot@10gen.com>
Date: Thu, 10 Sep 2009 00:39:30 -0400
Subject: sharding config db versioning SHARDING-33

---
 s/config.cpp | 44 ++++++++++++++++++++++++++++++++++++++++++++
 s/config.h   | 12 +++++++++++-
 s/server.cpp |  8 +++++++-
 3 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/s/config.cpp b/s/config.cpp
index b830b83664a..51334d79b47 100644
--- a/s/config.cpp
+++ b/s/config.cpp
@@ -29,6 +29,8 @@
 
 namespace mongo {
 
+    int ConfigServer::VERSION = 2;
+
     /* --- DBConfig --- */
 
     string DBConfig::modelServer() {
@@ -314,6 +316,48 @@ namespace mongo {
         
         return true;
     }
+    
+    int ConfigServer::dbConfigVersion(){
+        ScopedDbConnection conn( _primary );
+        int version = dbConfigVersion( conn.conn() );
+        conn.done();
+        return version;
+    }
+    
+    int ConfigServer::dbConfigVersion( DBClientBase& conn ){
+        auto_ptr<DBClientCursor> c = conn.query( "config.version" , BSONObj() );
+        int version = 0;
+        if ( c->more() ){
+            BSONObj o = c->next();
+            version = o["version"].numberInt();
+            uassert( "should only have 1 thing in config.version" , ! c->more() );
+        }
+        else {
+            if ( conn.count( "config.shard" ) || conn.count( "config.databases" ) ){
+                version = 1;
+            }
+        }
+        
+        return version;
+    }
+    
+    int ConfigServer::checkConfigVersion(){
+        int cur = dbConfigVersion();
+        if ( cur == VERSION )
+            return 0;
+        
+        if ( cur == 0 ){
+            ScopedDbConnection conn( _primary );
+            conn->insert( "config.version" , BSON( "version" << VERSION ) );
+            pool.flush();
+            assert( VERSION == dbConfigVersion( conn.conn() ) );
+            conn.done();
+            return 0;
+        }
+
+        log() << "don't know how to upgrade " << cur << " to " << VERSION << endl;
+        return -8;
+    }
 
     string ConfigServer::getHost( string name , bool withPort ){
         if ( name.find( ":" ) ){
diff --git a/s/config.h b/s/config.h
index 9e34c9fc243..edf813cce64 100644
--- a/s/config.h
+++ b/s/config.h
@@ -29,7 +29,7 @@
 #include "shardkey.h"
 
 namespace mongo {
-
+    
     class Grid;
     class ConfigServer;
 
@@ -150,6 +150,16 @@ namespace mongo {
            call at startup, this will initiate connection to the grid db 
         */
         bool init( vector<string> configHosts , bool infer );
+        
+        int dbConfigVersion();
+        int dbConfigVersion( DBClientBase& conn );
+
+        /**
+         * @return 0 = ok, otherwise error #
+         */
+        int checkConfigVersion();
+        
+        static int VERSION;
 
     private:
         string getHost( string name , bool withPort );
diff --git a/s/server.cpp b/s/server.cpp
index 8a8177498f4..f878c1372c8 100644
--- a/s/server.cpp
+++ b/s/server.cpp
@@ -164,8 +164,14 @@ int main(int argc, char* argv[], char *envp[] ) {
         cerr << "couldn't connectd to config db" << endl;
         return 7;
     }
-
+    
     assert( configServer.ok() );
+    
+    int configError = configServer.checkConfigVersion();
+    if ( configError ){
+        cerr << "config server error: " << configError << endl;
+        return configError;
+    }
 
     init();
     start();
-- 
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